Recently, there has been an increasing interest in energy storage technology. Electrochemical devices have been widely used as energy sources in the fields of cellular phones, camcorders, notebook computers, PCs and electric cars, resulting in intensive research and development into them. In this regard, electrochemical devices are one of the subjects of great interest. Particularly, development of rechargeable secondary batteries has been the focus of attention.
The electrochemical devices have been improved in their various performances, particularly, output, through consistent research. Among currently available secondary batteries, lithium secondary batteries developed in the early 1990's have drawn particular attention due to their advantages of higher operating voltages and much higher energy densities than conventional aqueous electrolyte-based batteries such as Ni-MH and the like. However, such lithium secondary batteries suffer from safety problems such as fire and explosion, according to use environment.
In order to overcome the safety problems of disadvantages of lithium secondary batteries, there is still a need to develop a binder that can increase a binding forcer between electrodes and a separator, particularly, a porous coating layer in the separator to induce strong integration of the electrodes and the separator, thereby strengthening safety, and can inhibit a resistance increase in interfaces between the electrodes and the separator, which may be generated by the side reaction of the electrodes during charging and discharging cycles, and also can improve air permeability, and for a separator using the binder.